Parental Behaviors in Rats and Mice

Joseph S. Lonstein1, Alison S. Fleming2

1 University of Massachusetts, Amherst, Massachusetts, 2 University of Toronto at Massachusetts, Mississauga, Ontario, Canada
Publication Name:  Current Protocols in Neuroscience
Unit Number:  Unit 8.15
DOI:  10.1002/0471142301.ns0815s17
Online Posting Date:  February, 2002
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Abstract

Parental care in mammals is often critical for survival and development of the offspring. The multiple behaviors that comprise parental care in rats and mice are controlled by a complex array of factors. This unit describes the components of parental care in rats and mice and the frequently used methods to assess the performance of these behaviors, a subject's preference for pupÔÇÉrelated cues, as well as a subject's motivation to act parentally.

     
 
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Table of Contents

  • Description of Parental Behaviors
  • Basic Protocol 1: Assessment of Parental Behaviors Using Direct Periodic Spot‐Check Observation
  • Basic Protocol 2: Assessment of Parental Behaviors Using Continuous Observation
  • Basic Protocol 3: Assessment of Nest Construction
  • Alternate Protocol 1: Assessment of Nest Construction—Mice
  • Basic Protocol 4: Assessment of Retrieval
  • Basic Protocol 5: Induction and Assessment of Parental Behavior in Nonlactating Rats and Mice (Sensitization)
  • Basic Protocol 6: Hormonal Induction of Maternal Behavior in Virgin Rats
  • Assessment of Maternal Preferences and Motivation in Rats and Mice
  • Basic Protocol 7: Test of the Unconditioned Preference for Pups or Pup‐Related Cues
  • Basic Protocol 8: Conditioned Place Preference Tests
  • Basic Protocol 9: Tests of Operant Responding
  • Basic Protocol 10: Using a T‐Maze Extension of the Home Cage to Assess Maternal Motivation
  • Commentary
  • Figures
     
 
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Materials

Basic Protocol 1: Assessment of Parental Behaviors Using Direct Periodic Spot‐Check Observation

  Materials
  • Parental lactating or nonlactating rodent subject
  • Litter of 1‐ to 8‐day‐old pups provided by a lactating “donor” animal (there are usually 6 to 8 pups in a culled litter, with equal numbers of males and females included)
  • Clear glass or polypropylene home and testing cage (for rats: ∼48 × 28 × 16 cm; for mice: 21 × 16 × 13 cm) with wood chips or shavings for bedding (∼8 cups for rats, 4 cups for mice). Cotton balls or pads can be used for mice.
  • Paper data sheets with each minute of the observation separated into 5‐, 10‐ or 15‐sec periods. Each sheet is divided into columns that represent time periods and rows that represent the individual behaviors.
  • Stopwatch

Basic Protocol 2: Assessment of Parental Behaviors Using Continuous Observation

  Materials
  • Parental lactating or nonlactating rodent subject
  • Litter of 1‐ to 8‐day‐old pups provided by a lactating “donor” animal (there are usually 6 to 8 pups in a culled litter, with equal numbers of males and females included)
  • Clear polypropylene pan cage (for rats: ∼48 × 28 × 16 cm; for mice: 21 × 16 × 13 cm) with wood chips or shavings for bedding (∼8 cups for rats, 4 cups for mice). Cotton balls or pads can be used for mice.
  • Humid incubator set at nest temperature (∼34°C)
  • Plastic or glass dish to hold pups
  • Cotton swabs
  • Small animal scale
  • Laptop computer
  • Data acquisition software that allows continuous recording of events at least once every second; available commercially (e.g., Noldus Observer, Noldus Information Technology; or Behavior Evaluation Strategies and Taxonomies software, Scolari, Sage Publications Software) although a rather simple data acquisition program may be generated in‐house by a person with some computer programming experience

Basic Protocol 3: Assessment of Nest Construction

  Materials
  • Parental lactating or nonlactating rodent subject
  • Litter of 1‐ to 8‐day‐old pups provided by a lactating “donor” animal (there are usually 6 to 8 pups in a culled litter, with equal numbers of males and females included)
  • Clear glass or polypropylene home and testing cage (for rats: ∼48 × 28 × 16 cm; for mice: 21 × 16 × 13 cm) with wood chips or shavings for bedding (∼8 cups for rats, 4 cups for mice). Cotton balls or pads can be used for mice.
  • Two‐ply paper towels (16 × 25 cm) shredded into thin strips

Alternate Protocol 1: Assessment of Nest Construction—Mice

  Materials
  • Parental lactating or nonlactating mouse subject
  • Clear glass or polypropylene home and testing cage (21 × 16 × 13 cm)
  • Cotton balls or pads (e.g., Nestlet squares)

Basic Protocol 4: Assessment of Retrieval

  Materials
  • Parental lactating or nonlactating rodent subject
  • Litter of 1‐ to 8‐day‐old pups provided by a lactating “donor” animal (there are usually 6 to 8 pups in a culled litter, with equal numbers of males and females included)
  • Clear glass or polypropylene home and testing cage (rats: ∼48 × 28 × 16 cm; mice: 21 × 16 × 13 cm) with wood chips or shavings for bedding (∼8 cups for rats, 4 cups for mice), with floor of cage divided by 1‐in. high plastic barriers into four equally‐sized quadrants to prevent the pups from crawling to the subject. Cotton balls or pads can be used for mice.
  • Stopwatch

Basic Protocol 5: Induction and Assessment of Parental Behavior in Nonlactating Rats and Mice (Sensitization)

  Materials
  • Nonlactating rodent subject
  • Unmanipulated lactating rats that can provide 1‐ to 8‐day‐old litters of test pups and that can foster any hungry pups (the total number of surrogate lactating dams necessary to provide recently fed pups each morning and feed hungry foster pups is approximately the same as the number of subjects that are actually being sensitized)
  • Clear glass or polypropylene home and testing cage (for rats: ∼48 × 28 × 16 cm; for mice: 21 × 16 × 13 cm) with wood chips or shavings for bedding (∼8 cups for rats, 4 cups for mice). Cotton balls or pads can be used for mice.
  • Stopwatch

Basic Protocol 6: Hormonal Induction of Maternal Behavior in Virgin Rats

  Materials
  • Adult female rats
  • Crystalline estradiol
  • Crystalline progesterone
  • Clear glass or polypropylene home and testing cage (for rats: ∼48 × 28 × 16 cm; for mice: 21 × 16 × 13 cm) with wood chips or shavings for bedding (∼8 cups for rats, 4 cups for mice). Cotton balls or pads can be used for mice.
  • Additional reagents and equipment for bilateral ovariectomy (unit 8.2, protocol 4) and subcutaneous implant of hormone capsules (unit 8.2, protocol 5)

Basic Protocol 7: Test of the Unconditioned Preference for Pups or Pup‐Related Cues

  Materials
  • Rat or mouse subject
  • Pups (six 1‐ to 3‐day old pups) or pup‐related olfactory cues (4 ounces of clean nest‐material on which pups have been placed for 6 to 12 hr, or onto which pup urine has been excreted); if nest material is used, use the same and standardized amounts of nest material during all tests
  • Test arena (Fig. A): glass or Plexiglas aquarium (90 × 45 × 47 cm) divided into two goal areas (areas A and B; each 15 cm) at either end and two center areas, A1 (adjacent to A; 30 cm) and B1 (adjacent to B; 30 cm)
  • Clear Plexiglas cube (8 × 8 × 8 cm) with perforated sides, top, and bottom (top removable to permit insertion of stimuli)
  • Glass bowls (∼8 cm diameter × 3 cm high) to hold nest material
  • Control stimuli: six small pink pencil erasers or control non‐pup related olfactory cues (4 ounces of clean nest material on which juvenile animals or adult animals have been placed for a 6‐ to 12‐hr period, or onto which urine has been excreted); if nest material is used, use the same and standardized amounts of nest material during all tests
  • Data acquisition software that allows continuous recording of events at least once every second; available commercially (e.g., Noldus Observer, Noldus Information Technology; or Behavior Evaluation Strategies and Taxonomies software, Scolari, Sage Publications Software) although a rather simple data acquisition program may be generated in‐house by a person with some computer programming experience

Basic Protocol 8: Conditioned Place Preference Tests

  Materials
  • Pregnant female rat subjects housed individually in polypropylene cages (∼48 × 28 × 16 cm) with wood chips or shavings for bedding
  • 70% ethanol
  • Large plastic weighing containers (weigh boats)
  • CPP apparatus (see above)

Basic Protocol 9: Tests of Operant Responding

  Materials
  • Rat test subject housed individually in polypropylene cages (∼48 × 28 × 16 cm) with wood chips or shaving for bedding (∼8 cups)
  • Kellogg's brand Froot Loop breakfast cereal, or similar food reward
  • 1‐ to 3‐day old rat pups
  • White noise generator or radio
  • Modified operant chamber (see description above)
  • Computerized system to automate the operant schedule and deliver stimuli according to the specified response schedule
  • Desk lamps with red light bulbs for nighttime observation
NOTE: The initial training phase consists of habituation, shaping, and conditioning phases using the food reinforcer. Follow these by the pup test phase and an extinction phase.

Basic Protocol 10: Using a T‐Maze Extension of the Home Cage to Assess Maternal Motivation

  Materials
  • Rat test subject housed individually in a polypropylene cage (∼48 × 28 × 16 cm) with wood chips or shavings for bedding (∼8 cups) with 10 × 10–cm hole in wall to accommodate T‐maze and which can be kept closed until testing (Fig. )
  • Neutral stimulus (e.g., small pink pencil erasers)
  • T‐maze (10 cm width; 10 cm height; 33 cm stem length, 37 cm arm length) fitting into hole in subject's home cage (Fig. )
  • 1‐ to 8‐day‐old rat pups
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Figures

Videos

Literature Cited

Literature Cited
   Bridges, R.S. 1984. A quantitative analysis of the roles of dosage, sequence, and duration of estradiol and progesterone exposure in the regulation of maternal behavior in the rat. Endocrinology 114:930‐940.
   Bridges, R.S., Zarrow, M.X., Gandelman, R., and Denenberg, V.H. 1972. Differences in maternal responsiveness between lactating and sensitized rats. Dev. Psychobiol. 5:123‐127.
   Deviterne, D. and Desor, D. 1990. Selective pup retrieving by mother rats: Sex and early development characteristics as discrimination factors. Dev. Psychobiol. 23:361‐368.
   Fleming, A.S. and Corter, C. 1995. Psychobiology of maternal behavior in non‐human mammals: Role of sensory, experiential and neural factors. In Handbook of Parenting (M. Bornstein, ed.) pp. 59‐86. L. Erlbaum Associates, New Jersey.
   Fleming, A.S. and Rosenblatt, J.S. 1974. Maternal behavior in the virgin and lactating rat. J. Comp. Physiol. Psychol. 86:957‐972.
   Fleming, A.S., Korsmit, M., and Deller, M. 1994. Rat pups are potent reinforcers to the maternal animal:Effects of experience, parity, hormones and dopamine function. Psychobiology 22:44‐53.
   Gandelman, R. and Simon, N.G. 1978. Spontaneous pup‐killing by mice in response to large litters. Dev. Psychobiol. 11:235‐241.
   Jakubowski, M. and Terkel, J. 1985. Incidence of pup killing and parental behavior in virgin female and male rats (Rattus norvegicus): Differences between Wistar and Sprague‐Dawley stocks. J. Comp. Psychol. 99:93‐97.
   Kalinichev, M., Rosenblatt, J.S., and Morrell, J.I. 2000. The medial preoptic area, necessary for adult maternal behavior in rats, is only partially established as a component of the neural circuit that supports maternal behavior in juvenile rats. Behav. Neurosci. 114:196‐210.
   Lee, A., Clancy, S., and Fleming, A.S. 2000. Mother rats bar‐press for pups:Effects of lesions of the mpoa and limbic sites on maternal behavior and operant responding for pup‐reinforcement. Behav. Brain Res. 108:215‐231.
   Lonstein, J.S. and De Vries, G.J. 1999. Comparison of the parental behavior of pairbonded male and female prairie voles (Microtus ochrogaster). Physiol. Behav. 66:33‐40.
   Lonstein, J.S. and De Vries, G.J. 2000. Sex differences in the parental behavior of rodents. Neurosci. Biobehav. Rev. 24:669‐686.
   Lonstein, J.S., Simmons, D.A., and Stern, J.M. 1998. Functions of the caudal periaqueductal gray in lactating rats: Kyphosis, lordosis, maternal aggression and fearfulness. Behav. Neurosci. 112:1502‐1518.
   Lonstein, J.S., Wagner, C.K., and De Vries, G.J. 1999. Comparison of the “nursing” and other parental behaviors of nulliparous and lactating female rats. Horm. Behav. 36:242‐251.
   Marques, J.M. 1979. Roles of the main olfactory and vomeronasal systems in the response of the female hamster to young. Behav. Neural Biol. 26:311‐329.
   Mayer, A.D. and Rosenblatt, J.S. 1980. Hormonal interaction with stimulus and situational factors in the initiation of maternal behavior in nonpregnant rats. J. Comp. Physiol. Psychol. 94:1040‐1059.
   Moore, C.L. and Morelli, G.A. 1979. Mother rats interact differently with male and female offspring. J. Comp. Physiol. Psychol. 93:677‐684.
   Numan, M. 1994. Maternal behavior. In The Physiology of Reproduction, 2nd ed. (E. Knobil and J.D. Neill, eds.) pp. 221‐302. Raven Press, New York.
   Quadagno, J.M., De Bold, J.F., Gorzalka, B.B., and Whalen, R.E. 1974. Maternal behavior in the rat: Aspects of concaveation and neonatal androgen treatment. Physiol. Behav. 12:1071‐1074.
   Rees, S. and Fleming, A.S. 2001. How early maternal separation and juvenile experience with pups affect maternal behavior and emotionality in adult postpartum rats. Animal Learn. Behav. 29:221‐233.
   Rosenblatt, J.S. and Lehrman, D.S. 1963. Maternal behavior in the laboratory rat. In Maternal Behavior in Mammals (H.E. Rheingold, ed.), pp. 8‐57. John Wiley & Sons, New York.
   Soroker, V. and Terkel, J. 1988. Changes in incidence of infanticidal and parental responses during the reproductive cycle in male and female wild mice Mus musculus. Anim. Behav. 36:1275‐1281.
   Stern, J.M. 1996. Somatosensation and maternal care in Norway rats. In Parental Care: Evolution, Mechanisms, and Adaptive Significance. Advances in the Study of Behavior, vol. 25, pp. 243‐294. (J.S. Rosenblatt and C.T. Snowden, eds.) Academic Press, New York.
   Stern, J.M. 1997. Trigeminal lesions and maternal behavior in Norway rats. III. Experience with pups facilitates recovery. Dev. Psychobiol. 30:115‐126.
   Stern, J.M. and Levine, S. 1972. Pituitary‐adrenal activity in the post‐parturient rats in the absence of suckling stimulation. Horm. Behav. 3:237‐246.
   Stern, J.M. and Lonstein, J.S. 1996. Nursing behavior is impaired in a small nestbox and with hyperthermic pups. Dev. Psychobiol. 29:101‐122.
   Stern, J.M. and MacKinnon, D.A. 1978. Sensory regulation of maternal behavior in rats: Effects of pup age. Dev. Psychobiol. 11:579‐586.
   Terkel, J. and Rosenblatt, J.S. 1971. Aspects of nonhormonal maternal behavior in the rat. Horm. Behav. 2:161‐171.
   Weisner, B.P. and Sheard, N.M. 1933. Maternal Behavior in the Rat. Oliver and Boyd, Edinburgh, U.K.
   Wilsoncroft, V.E. 1969. Babies by bar‐press: Maternal behavior in the rat. Behav. Res. Methods Instrum. 1:229‐230.
Key References
   Fleming et al., 1994. See above.
  Discusses the many factors that affect the formation of a conditioned place preference for pup reward.
   Lee et al., 2000. See above.
  Discusses operant responding for pup reward in postpartum and non‐postpartum maternal and nonmaternal animals, as well as effects of lesions in brain on operant responding.
   Fleming, A.S., Cheung, U., Myhal, N., and Kessler, Z. 1989. Effects of maternal hormones on “timidity” and attraction to pup‐related odors in female rats. Physiol. Behav. 46:449‐453.
  Describes the procedures and the background for the use of open‐field and olfactory preference testing to assess “emotionality” and “preferences.”
   Fleming and Corter, 1995. See above.
  Provides an excellent overall review of the biology and factors influencing maternal behavior in rodents.
   Numan, 1994. See above.
  An excellent review that provides a very detailed, accurate, and comprehensive review of studies relating to the psychobiology of maternal behavior.
   Sharpe, T.L. and Koperwas, J. 2000. Software assist for education and social science settings: Behavior evaluation strategies and taxonomies (BEST) and accompanying qualitative applications. Sage‐Scolari Publishing. Thousand Oaks, CA.
  The data acquisition system preferred by the authors.
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